• Gerald C Ihra, Andreas Heid, and Thomas Pernerstorfer.
• Department of Anesthesiology, Medical University Vienna, Vienna, Austria. gerald.ihra@meduniwien.ac.a
• Anesth. Analg. 2009 Aug 1;109(2):461-5.

BackgroundHigh-frequency jet ventilation (HFJV) can lead to high-airway pressures under certain conditions. In this laboratory study, we evaluated the influence of the injector's position relative to a fixed airway obstruction on peak pressures in a tracheal-lung model.MethodsWe administered HFJV via a metal jet injector at varying distances from connectors simulating laryngotracheal airway stenosis. Peak pressures were measured inside the lung model.ResultsWhen the jet nozzle was near the simulated stenosis, peak pressure within the test lung increased and reached a maximum when the stenosis' lumen decreased despite unchanged parameters of jet gas flow. With the injector's tip placed 8-10 cm in front of the stenosis, reduction of airway diameter did not result in an increase of distal peak pressures. These observations were similar for all settings of gas flow (0.5-1.5 bar driving pressure) and frequencies.ConclusionThis study in a lung model suggests that placing an injector more than 8 cm proximal to a laryngotracheal stenosis will prevent changes in intrapulmonary pressure related to the degree of stenosis or driving pressure during HFJV. The location of the injector chosen for clinical care should balance the need for effective ventilation with the risk of barotrauma.

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